The present invention pertains generally to the field of generator sets. In particular, the present invention pertains to engine controls for generator sets used to power heating and cooling devices for controlling the temperature of cargo containers.
Containerized shipment of goods has become a widely accepted means of transporting cargo around the world. Modern containers can be stacked on the decks of a ship for shipment overseas. When a container ship arrives at a port, the containers can be efficiently removed from the shipment by crane. At the port, the containers can be stacked for further ship by truck or rail. When the containers are shipped by truck, a single container is usually placed on a semi-trailer chassis. Each rail car generally can support up to four containers.
When the cargo includes perishables such as food stuffs or flowers, the temperature in each of the containers must be controlled to prevent loss of the cargo during shipment. For shipments of perishable goods, specialized containers have been developed which include temperature control units for refrigeration and/or heating. While on board ship, the containers can be connected to a ship's generator for power to the temperature control units. When the containers are in port, they may be connected to a power source provided by a local utility.
When, however, the containers are in transit by railcar or truck, generator sets must be provided to power the temperature control units. Such generator sets usually include a diesel engine to power a generator which in turn provides electric power to the temperature control units. Such generator sets can be clipped directly to a container or fastened to a trailer chassis.
During shipment, the temperature control units and generator sets must operate for extended periods of time. For example, when lettuce is shipped from California to the northeastern United States, the sets may run periodically for several days. During this extended period of time, the temperature control unit and generator set will operate for extended periods without inspection by transportation workers. This is particularly true in the case of rail transportation where scores of railcars may, for extended periods, be in transport while accompanied by only two or three workers.
During these extended periods when the temperature control units and generator sets are substantially unmonitored by transportation workers, the generator sets may experience "nuisance" shutdowns, causing a loss of power to the temperature control unit. This may result in a loss of the perishable cargo. This is particularly true if ambient temperature conditions are very hot or very cold. A nuisance shutdown is usually caused by a transitive condition which may exist briefly, but does not involve a chronic generator set problem which will persist when the transitive condition abates. Thus, the engine or generator set could be restarted if an operator notices that the shutdown had occurred.
In addition to nuisance shutdowns, the generator may shutdown for a non-transitive cause. For example, there may be a chronic generator set problem such as loss of engine coolant. In such a case, the generator could not be safely restarted without risking permanent damage to the engine.
As providing a consistent source of power to the container temperature control units is essential if the loss of perishable cargo is to be prevented, a number of methods and apparatus have been proposed for controlling generators. None of the these, however, have addressed the serious problem of correcting generator set nuisance shutdowns during an extended period where the generator set is unattended. Further, they have inadequately dealt with non-transitive causes of engine shutdowns.
U.S. Pat. No. 5,390,068 to Schultz et al. discloses a microprocessor based generator set controller apparatus and method which monitors various engine and generator faults and uses the generated signals to control the operation and output of the engine generator system. Schultz et al. also discloses the controller includes self diagnostic and serial communications ports.
U.S. Pat. No. 5,561,330 to Crook discloses an automatic electric power generator control that automatically starts the generator engine and the generator when a demand is made for electric power. U.S. Pat. No. 4,853,553 to Hosie discloses a control system for controlling electric generating apparatus including electrically heated combustion engines. Finally, U.S. Pat. No. 4,463,305 to Wineland et al. discloses a method and system for delaying mechanical loading of an internal combustion engine by an alternator during startup of the engine by inhibiting the field winding current of the alternator until the engine reaches a predetermined operational condition.
Thus, what has not heretofore been provided is a method and apparatus for restarting an unattended, nuisance shutdown generator set. Further, prior methods and apparatus have inadequately served to prevent engine shutdowns for non-transitive causes. Such an apparatus would provide substantial advantages in the field of container shipment and particularly in the container shipment of perishable items.